Drug delivery devices for setting and dispensing a single or multiple doses of a liquid medicament are as such well-known in the art. Generally, such devices have substantially a similar purpose as that of an ordinary syringe.
Drug delivery devices, in particular pen-type injectors have to meet a number of user-specific requirements. For instance, with patient's suffering chronic diseases, such like diabetes, the patient may be physically infirm and may also have impaired vision. Suitable drug delivery devices especially designed and intended for home medication therefore need to be robust in construction and should be easy to use. Furthermore, manipulation and general handling of the device and its components should be intelligible and easy understandable. In particular setting and dispensing of a dose of the medicament should be easy to conduct and has to be safe and reliable.
Typically, such drug delivery devices comprise a housing adapted to receive a cartridge at least partially filled with the medicament to be dispensed. The device further comprises a drive mechanism, typically having a displaceable piston rod which is adapted to operably engage with a piston of the cartridge. By means of the drive mechanism and its piston rod, the piston of the cartridge can be displaced in a distal or dispensing direction and may therefore expel a pre-defined amount of the medicament via a piercing assembly which is to be releasably coupled with a distal end section of the housing of the drug delivery device, e.g. with a cartridge holder.
In particular with users or patients being physically or visually impaired correct handling of the device is sometimes cumbersome. Moreover, especially prior or after replacement of an empty cartridge, the patient has to be informed, that an initial or final dose is to be set and dispensed or that an initiating priming procedure has to be conducted. Moreover, the device may provide visual or readable indicators or display elements in order to inform the user or patient of the actual status and configuration of the device. Such information should be clearly and unambiguously legible, even for visually impaired persons.
Document DE 101 06 367 A1 for instance discloses a pen-type injector comprising a magnifying optic to support reading of a dose scale.
Moreover, document WO 2010/020311 A1 discloses a first and a second lens arrangement mutually acting together to increase the legibility of a set dosage value, preferably to counteract false readings of a selected dosage setting.
Such optical aids may enhance secure and safe handling as well as operation of drug delivery devices. However, visual illustration of different device states always requires a comparatively large mutual displacement of optical aids and display members carrying the information to be displayed and/or magnified. Typically, spatial relative displacement of the various components is at least in the range of the size of the information to be displayed.
It is therefore an object of the present invention to provide an improved display arrangement adapted to display different configurations or device states on the basis of a minimum displacement of a display member and an optical aid. Moreover, the display arrangement according to the present invention should be robust, reliable as well as cost efficient in terms of manufacturing and assembly. Also, the display arrangement should be easily legible and should visually provide different information with a large contrast.